/*
 * Copyright 2020 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#ifndef SkottieKeyframeAnimator_DEFINED
#define SkottieKeyframeAnimator_DEFINED

#include "include/core/SkCubicMap.h"
#include "include/core/SkPoint.h"
#include "include/private/base/SkNoncopyable.h"
#include "modules/skottie/include/Skottie.h"
#include "modules/skottie/src/animator/Animator.h"

#include <vector>

namespace skjson {
class ArrayValue;
class ObjectValue;
class Value;
} // namespace skjson

namespace skottie::internal {
class AnimationBuilder;

struct Keyframe {
    // We can store scalar values inline; other types are stored externally,
    // and we track them by index.
    struct Value {
        enum class Type {
            kIndex,
            kScalar,
        };

        union {
            uint32_t idx;
            float flt;
        };

        bool equals(const Value &other, Type ty) const
        {
            return ty == Type::kIndex ? idx == other.idx : flt == other.flt;
        }
    };

    float t;
    Value v;
    uint32_t mapping; // Encodes the value interpolation in [KFRec_n .. KFRec_n+1):
                      //   0 -> constant
                      //   1 -> linear
                      //   n -> cubic: cubic_mappers[n-2]

    inline static constexpr uint32_t kConstantMapping = 0;
    inline static constexpr uint32_t kLinearMapping = 1;
    inline static constexpr uint32_t kCubicIndexOffset = 2;
};

class KeyframeAnimator : public Animator {
public:
    ~KeyframeAnimator() override;

    bool isConstant() const
    {
        SkASSERT(!fKFs.empty());

        // parseKeyFrames() ensures we only keep a single frame for constant properties.
        return fKFs.size() == 1;
    }

protected:
    KeyframeAnimator(std::vector<Keyframe> kfs, std::vector<SkCubicMap> cms)
        : fKFs(std::move(kfs)), fCMs(std::move(cms))
    {}

    struct LERPInfo {
        float weight; // vrec0/vrec1 weight [0..1]
        Keyframe::Value vrec0, vrec1;
    };

    // Main entry point: |t| -> LERPInfo
    LERPInfo getLERPInfo(float t) const;

private:
    // Two sequential KFRecs determine how the value varies within [kf0 .. kf1)
    struct KFSegment {
        const Keyframe *kf0;
        const Keyframe *kf1;

        bool contains(float t) const
        {
            SkASSERT(!!kf0 == !!kf1);
            SkASSERT(!kf0 || kf1 == kf0 + 1);

            return kf0 && kf0->t <= t && t < kf1->t;
        }
    };

    // Find the KFSegment containing |t|.
    KFSegment find_segment(float t) const;

    // Given a |t| and a containing KFSegment, compute the local interpolation weight.
    float compute_weight(const KFSegment &seg, float t) const;

    const std::vector<Keyframe> fKFs;                         // Keyframe records, one per AE/Lottie keyframe.
    const std::vector<SkCubicMap> fCMs;                       // Optional cubic mappers (Bezier interpolation).
    mutable KFSegment fCurrentSegment = { nullptr, nullptr }; // Cached segment.
};

class AnimatorBuilder : public SkNoncopyable {
public:
    virtual ~AnimatorBuilder();

    virtual sk_sp<KeyframeAnimator> makeFromKeyframes(const AnimationBuilder &, const skjson::ArrayValue &) = 0;

    virtual sk_sp<Animator> makeFromExpression(ExpressionManager &, const char *) = 0;

    virtual bool parseValue(const AnimationBuilder &, const skjson::Value &) const = 0;

protected:
    explicit AnimatorBuilder(Keyframe::Value::Type ty) : keyframe_type(ty) {}

    virtual bool parseKFValue(const AnimationBuilder &, const skjson::ObjectValue &, const skjson::Value &,
        Keyframe::Value *) = 0;

    bool parseKeyframes(const AnimationBuilder &, const skjson::ArrayValue &);

    std::vector<Keyframe> fKFs;   // Keyframe records, one per AE/Lottie keyframe.
    std::vector<SkCubicMap> fCMs; // Optional cubic mappers (Bezier interpolation).

private:
    uint32_t parseMapping(const skjson::ObjectValue &);

    const Keyframe::Value::Type keyframe_type;

    // Track previous cubic map parameters (for deduping).
    SkPoint prev_c0 = { 0, 0 }, prev_c1 = { 0, 0 };
};

template <typename T> T Lerp(const T &a, const T &b, float t)
{
    return a + (b - a) * t;
}
} // namespace skottie::internal

#endif // SkottieKeyframeAnimator_DEFINED
